Ultrasound findings in 46 cases of incomplete release of the transverse carpal ligament in carpal tunnel surgery

Purpose: To describe the ultrasound (US) features of a complication in patients who have undergone surgery for carpal tunnel syndrome (CTS): the incomplete release of the transverse carpal ligament (TCL). Materials and Methods: Reports from two institutions were searched using the keywords "persistent CTS" and "incomplete TCL release". Post-surgical US examinations were performed using a standardized approach at both institutions, first assessing the muscles supplied by the median nerve (MN) and then conducting a detailed evaluation of the MN course at the wrist. To avoid misinterpreting ligament regrowth, patients with recurrent symptoms two months or later after surgery were excluded. Only cases showing clear compression by the TCL were selected. Results: A total of 46 patients were identified with incomplete release of the TCL, with the average uncut portion of the ligament measuring 6.7 mm. The proximal margin of the TCL was incompletely released in 65% of the cases, while the distal margin was affected in 35%. Symptoms in these patients persisted after surgery, and, in 52%, they were worse than before surgery. A reduction in thenar muscle bulk was observed in 37 patients. Follow-up clinical data were available in eight patients, with three undergoing US evaluation after revision surgery. Conclusion: US can effectively demonstrate the incomplete release of the TCL, visualized as a fibrillar uncut structure compressing the MN and producing an hourglass appearance of the nerve. In addition, US may help detect other factors that contribute to persistent symptoms and help to guide revision surgery.